Better idea: use Moosehunter's beautiful CLI: https://github.com/Thealexbarney/VGAudio
Converts between every Nintendo DSP format losslessly. It's a beautiful thing.
You said they're Switch BFSTMs--in that case you're going to want to build from the nintendo-ware branch, since Moose hasn't merged functionality for the new BFSTM fields in the main 2.0 branch yet.
But for future reference, at the top left of the project page, it should say "branch: 2.0." Click that and it'll bring up a list of the branches of the project; all you need to do is click the one you want (nintendo-ware in this case) and then download it. Also, Moosehunter kindly included a build script in the source, so if you have the VS redistributables, all you need to do is run build.cmd.