This depends on the plan you are on and the number of WordPress installs it includes.
Entry Plans:
Starter plan: 1 free migration
Pro Plan plan: 3 free migrations
Growth plan: 5 free migrations
Advanced plan: 8 free migrations
Agency Plans:
Freelancer plan: 12 free migrations
Agency 1 plan: 20 free migrations
Agency 2 plan: 30 free migrations
Agency 3 plan: 40 free migrations
Premium Sites Plans:
Premium Site 1 plan: 2 free migrations
Premium Site 2 plan: 2 free migrations
Premium Site 3 plan: 2 free migrations
Premium Site 4 plan: 2 free migrations