You tip it over while supporting the plant at the stem and carefully ease the pot up. If ya see a bunch of roots, it's time to transplant. If a bunch of dirt falls all over your arm, I was right and now you'd better transplant very carefully because you're about to shock the shit out of those little roots.
Hopefully I'm wrong, you'll see a root mass, and you can settle the pot back on until your bigger pot is ready.
Also search " transplant cannabis" on the YouTube, it's very helpful to watch so one do it, at least it was for me. Good luck