Hi @Biojim46, welcome to the community.
You can use a third party file manager as @Thomas79 suggested or the built in one in the phone under Settings > Storage > 3 dots > Advanced > Storage > SD Card.
You can also navigate and transfer your files between SD and Phone memory easily using a computer. If you connect your phone and select File transfer mode(MTP), you can access your phones storage like a portable storage device, such as a USB flash drive.
