Not to ignore you, but don't know how to help. When you say 'spade' connector--is that a metal end that fits into a slot? Might have to take back off of the manual new stat and there should be places for 3 or 4 wires. The furnace should have corresponding cable with 3 or 4 wires in a bundle--at least, that is what I am used to seeing. The individual wires are just telephone cable wires and you may be able to just cut the insulation off each wire and attach to the new stat.
Sorry, not much help...
And, welcome to the forum.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired