is their anyway to figure out how many troops someone has at a certain location without attacking them first.

you can use scans, they are never 100% but they give you an idea

click the colony, then the "eye" then military scan or advanced millitary scan

regular military scan give u a 50% sure number of how many units and what kind they are (inf/veh/tanks)
advanced give u a 25% sure number of how many units and what weaponds they have (conc, beam, explosive)

you need first spy building to do regular scans, third to make advanced military scans