Finally Ive found a gym with an actual power rack after being stuck with a smith machine for way too long-Monday will be my 1st day using it. Can I hope for much of a carryover to regular back squats?
It depends on how strong you got in the smith machine movement and whether you posses any weaknesses that were not addresses by squatting in the smith machine.
It really doesn't make sense to worry about this anyway. Just get under the bar and find out what you can lift by adding plates.
I'd expect quite a big drop in weights so start low and ramp up to see what the weights feel like. But you should improve pretty quickly once you get used to stabilizing the bar.