First you need to find where the game is storing those save files, mostly where game stores them depends on the engine, Ren'py in Appdata, RPGM in it's game "www/save" folder. Just google like " "Engine name" save file location ", it should tell you where to look. But most of the times games store save files in /AppData/Roaming.
As for how to transfer something from one PC to another if you dont have the USB flash or any other means, you can use any of the File hosting/sharing services like google drive or mega. Or something like DropMeFiles or pixeldrain.