You'd probably want to be squatting for a month at least beforehand. I say this bc form is very important with Sheiko and mainly bc the volume will leave you crippled at first and introducing squats in a Sheiko format to someone who hasn't done them for a while will not end well lol.
Sheiko is an intermediate/advanced routine. If you're not at this level it'll still work but faster progress could be made with simpler programming.
You can google Sheiko spreadsheet yes. 29 and 37 are prep blocks. 30 is a volume block, 31 is an intensity block, 32 is a peaking block, and there are a few others.