Well, the true scale of the internal migration is hard to gauge because Russia is Russia, but in classic fashion there's likely been quite a bit of forced migration but could be as many as 800,000 to 1,000,000 people who have been "brought" into Crimea one way or another and a number of native Ukrainians and Tatars have been forcibly relocated.

Edit: and I found one estimate putting the number of internally displaced Crimeans in Ukraine at 20,000 – 100,000 (pg. 2), but another estimate had an upper limit of 200,000