If the phone uses a simple sd card setup, it'll mount that as USB.
If it uses a portion of storage marked as an internal sd card, you'll need MTP for that.
MTP is a Windows protocol.
If you don't mind wifi, install SwiFTP for full access or any number of wifi-private-web (read: only on your network) solutions. AirDroid is a very good one.
I use MTP, SwiFTP, AirDroid (all free) and like MTP least of all, but your mileage may vary.
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