I was wondering how to convert the files for sfm models, such as .vtx, .phy, .mdl, and .vvd into a Blender 2.8 compatible format.
You'll first need to decompile the .mdl file into an .smd file. Crowbar is an excellent tool to decompile mdl files, find it here: Crowbar (Source Engine Modding Tool)
After that, you can use the Blender source tools as 8foldhero suggested: BlenderSourceTools
Install it as an addon like usual, and you'll be able to import any smd file into Blender by going to
File > Import > Source Engine (.smd, .vta, .dmx, .qc), then choose the file from the dialog box. I recommend changing the Bone Append Mode to
Make New Armature. Good Luck!
There are some guides on the SFM workshop and wiki on how to do it specifically (Here is one from the wikia in particular https://developer.valvesoftware.com/wiki/Blender_Source_Tools_Help )
but the most essential think is the "Blender Source Tools" add-on. You will need to install this into blender, and then from that (File > Import > Source Engine Filetypes)