change from hdd to ssd

I recently got a new SSD, and am trying to move all my files from my old hard drive onto it. In the samsung data migration software, it says I need addtional space on the target drive (about 68gb) despite the hard drive being 100gb under capacity. Both the disk and ssd are 1tb.

Here's the digital manual for my motherboard. Please tell me if I can run a M.2 SSD from this. I genuinely have no clue how to tell if I can or not. ECS H81H3-M I genuinely have no idea what to look for, and all the letters and numbers are confusing to me, so I don't even know what to match to...