Mark your cabinets on the wall and floor before you take them out... Just trace around them... You'll cut some of the floor out but it's nice to have as a reference for install... They probably used these cheap square drive screws to mount the cabinets like the few that I've worked on... They strip out rather easy and break... So that adds a level of fun to it... The cabinets aren't made to be moved around... Had some just fall apart from removal... Probably cause they got beat being in the trailer... So get them out the way and set them on a flat surface... I've seen a couple different ways the subfloor is mounted... Screwed to wood 2x3 carriage bolted to the frame every 24" spanning the width... Or the subfloor screwed directly to the angle iron frame every 24"... Either way block your seam in between with a 2x4 and screw that off... I prefer using a torx type screws when I can... A little more expensive then phillips or square head... If you have to connect directly to the metal they have 2" self tappers with a tapered head that will hold it down just fine with one every 6"... But the torx stay on the bit, drive so easy without wobbling, don't strip out, rarely break a tip... Screw the cabinets back in where they were screwed in or as close as possible without any extras added... Unless you know you're not going to hit anything that you may regret... Found that out once too... Either way it's a trailer and they are known for this... Probably way worse then what you see... It always turned into way more because they hide the rot very well...