Right, so to begin with, we need to disabuse ourselves of the notion that the 'Silk Road' ever existed. This recent answer by /u/Sankon and this older one by myself, both largely summarising aspects of Scott C. Levi's The Bukharan Crisis, should give a good sense of the problems with not just the framework behind your question, but also its specific aspects. In particular, long-distance, big-caravan trade was not the norm in terrestrial commerce in Central Asia, though it could certainly take place.

Babur (1483–1530), in his autobiographical geography the Baburnama, does report 'caravans of 'ten, fifteen, twenty thousand pack animals' travelling between India and Kabul, though it is worth noting that in general, large caravans were formed for purposes of security, rather than being indicative of booming trade. In more peaceful times, smaller caravans would be more willing to risk longer journeys. A particularly illustrative case of how such caravans were formed comes through Bento de Goës' reports from his time in Kabul around 1603/4. He notes that 'large' caravans from Kabul to China were assembled at most once a year when a large number of caravan drivers banded together to form a temporary association. Similarly, he reported that there was a roughly annual 'large' caravan from Lahore to Yarkand, consisting of 500 people forming temporarily for security. It was these smaller caravans, not their occasional consolidations, that were the building blocks of Eurasian land trade.

Paradoxically, though, quite what these smaller caravan sizes were was can be hard to determine. Valerie Hansen's 2012 study of the Silk Road offers a number of historical examples that suggest relatively low numbers of people and animals made up a caravan in the Late Antique period: looking at the thirteen surviving documents recording caravan sizes at Kucha between 641 and 644, the largest caravan contained 40 men, the next most 32, the next most 20; ten of the thirteen recorded caravans had ten men or fewer – though in one case, there were ten women and six men in a caravan. The number of animals was similarly small – often 1 animal per two people – and typically horses, donkeys and cattle rather than camels.

By the Early Modern period, caravans in Central Asia were very much camel-dominated, and their typical sizes tended to remain small. The Indian caravan that travelled to the Orenburg Fair in 1745 brought the equivalent of just sixty camels for instance, and this was a decidedly long-distance trip across Central Asia that netted them 300,000 roubles in revenue. But the rough ratio of people to camels seems hard to pin down precisely, with a typical minimum of two camels per person, but an unclear upper end. Similarly, the typical number of people per caravan is also hard to determine. It is true that we can point to examples like the Lahore-Yarkand caravan and say that larger caravans did exist – if camel-based, there might well have been as many as 2000-2500 camels in such a caravan, realistically. But I cannot stress enough the relative atypicality of such a situation. It took the Russian army 18 months to gather 10,000 camels together in 1839 from actively camel-breeding nomadic allies, and most of these ended up either starving or, more frequently, freezing to death in the winter of 1839/40. The likelihood that private interests in one locale, especially in the more integrated mercantile networks of northern India, could sustainably concentrate anywhere near a fraction of that number of animals at any one time was extremely low unless there were external factors incentivising such concentration.

It is important also to note that many Early Modern 'caravans' were in fact herds of livestock – often quite substantial ones – purchased from nomadic pastoralists for sale at farming cities, rather than of pack animals carrying dry cargo. For instance, one caravan venture in 1767 saw 252 horses, 487 cows and 8,330 sheep bought by Central Asian merchants from the Kazakhs and Kirghiz, and sold on at Ush-Turpan.

In other words, it is impossible to know for certain because there was never a standardised size of caravan. That doesn't mean we cannot speak of the rough carrying capacity per animal within a caravan: camels can realistically carry a maximum of between 150 and 200 kilograms, so for instance the sixty camel-loads at Orenburg might represent around 9 to 12 metric tonnes. But to translate that to TEUs isn't exactly going to cut it because, well, what is the density of the merchandise in question? To use two common sorts of merchandise, a TEU (23 cubic metres) of unprocessed cotton would weigh almost 36 tonnes, whereas a TEU of salt would weigh nearly 50. Essentially, we're working with different quantities with no control variable, and that's a bit of a no-no.

So have we come to a workable answer? Not really. But that's due in large part to a genuine paucity of known source material regarding short-distance caravan sizes that isn't just inferences. Especially because the revision in approaches to the 'Silk Road' concept is extremely recent as of writing, it will likely be in the near future that we may see a more precise, quantitative approach to caravan sizes.