Upvote:4
Slavic slaves were very common in Europe in Medieval times. One standard rout was Islamic slave trade from Balcans were the slaves were taken to the markets in Europe as far as Spain. Another rout began in what nowadays is Southern Ukraine, through Crimea, where the slaves were resold to Genoese traders.
The Scandinavian founders of the future states called Rus, descendents of the legendary Rurik, were essentially a family-owned slave trading company operating on the territory of modern Russia and Ukraine. They sold the slaves to the Muslims first, transporting them on Volga, and later in the Black sea area transporting on the Dnieper. Then, through several intermediaries, many slaves ended in Western Europe.
Sources: Очерки начальной Руси. Киев; СПб., 2015. Sorry, only in Russian.
https://en.wikipedia.org/wiki/Saqaliba
https://medium.com/the-history-buff/slavery-in-medieval-italy-cb189ae45933