Elias here with Shopify Support. I'd be happy to help you with this!
If you're looking to change the country from when you created your account, that's located in the General settings (Settings > General). However, if you have Shopify Payments enabled, then you'll need to disable Shopify Payments before you can change the country.
If you also need help with settings up taxes, we've got an amazing guide that may be able to help with that - Taxes.
Let me know if this is what you're looking for?