When to transition your toddler(s) to a bed?

La

I have twin boys that are almost a year and a half and they have slept in their pack and plays since we didn’t have cribs at the time since they were 3 months old. By the time we GOT cribs I honestly just didn’t want to put them in it bc of SIDS

Anyways when can they transition to big boy beds ? How did you do it?