Issue with specular map from House Furniture Pack

Hello I'm currently building a scenario with the House Furniture Pack I bought not long ago. I also have the Simple Corridor Pack as well and both of them take around 2Gb together therefore I can't upload it to my Unity Collab. Someone suggested me to convert the image's formats for the textures to .jpg so they won't take that much space.

The thing is I've converted the format to .jpg but when I open Unity it requires me to select one by one the different maps for the texture (Diffuse, Normal and Ambient Occlusion) but there's another one map that's ended by an "s" (Sofa_House_s) which I suppose it's Specular (?) and I don't certainly know where to add this map in the Unity Editor. If I'm not wrong I've added the rest to the correct maps:

Diffuse -> Albedo
Normal -> Normal
Ambient Occlusion -> Occlusion
Specular (?) -> (Where should I add it?)

Also if there's another way to re-do all the textures after changing the format instead of doing it one by one, I'll appreciate it so much. I'm starting using Unity just a few months ago so forgive my limited knowledge about the engine.

By the way I'm using Unity 2017.2.0f3.

Thank you in advance!