Is there a reason you can't create problem sets of all 4 sections and take them in LSAT conditions in their original order? If you want a score, I imagine that your performance on a preptest you have some memory of wouldn't be a perfectly accurate representation of your LSAT score, but after you finish the problem sets you could take the number you missed and compare it with the link below to find out.

https://www.powerscore.com/lsat/help/LSAT-raw-score-conversion.cfm