How can I password protect my SD card?

So that it will ask to enter password when I open the SD card from a computer or I reinsert the card.

Hum, not sure if you can. You can encrypt it. They may be an app that does that?

put a dot on of all your folders ie .music this will hide the folders from flle managers however you can use a file manager that allows you to see the hidden files when click on the option to show hidden files for example es file explorer is good