By the time that African slavery really got going, slavery had been abolished in most European countries.

So, there were not many Aftican slaves in Europe (though there would have been some, particularly in Spain, Portugal, and the European possessions of the Ottoman Empire). Those (few) African slaves that there were in Europe, would have generally not been plantation agricultural workers, but, more likely, domestic servants.

Slavery was not common in Europe from the 18th century (which is when the African slave trade really heated up).

It had been abolished in Iceland in 1117. The Magna Carta in England (of 1215) was interpreted by the courts (clause 30) as banning slavery in England. The town of Bologna in Italy abolished slavery in 1256. By 1274, slavery was abolished in Norway. In 1315, Louis X abolished slavery in France (though it continued in some degree in the South of France, along the Mediterranean until the 17th century. In 1335 Sweden made slavery illegal. In 1347 Poland abolished slavery. In 1588 Lithuania abolished slavery. In 1723, Russia abolished slavery. In 1761 Portugal abolished slavery in Portugal and Portuguese India.

So, there was almost no slavery (legally) in Europe by the late 18th century. There were some places where it had not been made illegal (Ireland, Scotland) but rarely existed. It was also not present in Germany, the low countries, Switzerland, and much of Italy, but the fragmentation of jurisdictions in those places means that tracking the dates of abolition would be complex.

I think slavery was still legal in Spain. But I don't think there were large numbers of slaves there.

The main slavery in Europe by the late 18th century was in the Ottoman Empire, where slavery was still practiced (though few of the slaves, in the European parts of the Empire would have been African, they were mostly European). The other exception was the Crimean Tartars. They made their last major slave raid into Russia in 1769, and held slaves until conquered by the Russians in 1783.

There may have still been slavery in the Caucasus.

The Barbary States, in North Africa, were also still seizing European ships and enslaving the crews and raiding European coastlines for slaves into the late 18th century.