Most people in Scandinavia were Western Christians (Catholics) in 1300 AD. Christian missions began to Scandinavia as early as the 8th century, and the number of Christians gradually rose through the growing population of Christian slaves. However, it wasn't until the 10th century that Scandinavian rulers began seriously converting. The most zealous 10th century Scandinavian Christian king was Olaf Tryggvason, or Olaf I of Norway. After his conversion in 995 he destroyed pagan temples and persecuted pagans. There was some pushback against this, but Norway was still rapidly Christianized, particularly under the reign of Olaf II, later known as Saint Olaf.

Things were a little slower in Sweden. The first Christian king was Olof Skötkonung, who became king in the 990s, but strong pagan elements remained through the 12th century. It's possible that this was also true in Norway and just goes less recorded, but in general the Swedish kings seem to have been less punitive towards paganism than the Norwegian ones.

In Iceland, Christianity actually predated paganism since the earliest inhabitants of the island were Irish monks. However, it was swept under Olaf Tryggvason's zeal for Christian conversion and officially converted in 1000, though pagan worship was still tolerated in private. Orkney had also been Christian before the Scandinavians came, as the evidence of Pictish Christian sculpture suggests. However, it was gradually re-Christianized in the 11th century.

Although there would still have been some pagan practices and even people who didn't identify as Christian at all in the early years of conversion, by 1300 almost everyone in Scandinavia would have been thoroughly Christianized. That doesn't mean they weren't still interested in their older stories and customs which we would describe as "pagan" -- almost all of our literature about the "pagan" past was written by Christians around this time.

However, there were still some people in Scandinavia in 1300 who were definitely not Christian. The Sámi were not at all Christian and are ethnically totally distinct from the rest of Scandinavia. There were laws forbidding Christian Scandinavians from consulting the Sámi for prophecies and other "magic". Similarly, Greenland is not part of Scandinavia but at the time had many Norse colonists. They were Christian, but their Indigenous Inuit neighbours were not. There was also the occasional Muslim traveller to Scandinavia who was not Christian, and there would have been pagans from other parts of Europe occasionally there for trade or other business. Overall though, all Norse people were Christian by 1300, but there were minority populations of Sámi and Inuit who lived in or near Scandinavian cultural zones but were not Christian.