Transferring .mp3 files (audio books) from my PC

[y2k3]

Hello, I'm new to the forum and also feels like new to the digital world so thanks for your patience if this is a very silly question. I have iPad Mini from 2~4 years ago. I have several .mp3 files ranging from 50MB to 200MB downloaded to my external hard drive. Those are audio books and I'd like to listen to them during my 2-hour commute. I used to be able to just email them when the files were much smaller, but anything beyond 20MB doesn't work very well. I do not have iTune account and prefer not to use iTune. Are there any more "analog" ways, like using USB cables, to connect 2 devices and transfer files? Also, I'd appreciate the recommended apps if I shouldn't be using the default program. Thanks Much!!!!