Your Tascam has phantom power built in, so don't limit yourself with a SM-57 or SM-58 dynamic mic. They are both excellent, but you'll be far better served if recording acoustic guitar to use a small diaphragm condenser.
The AKG P-170 is a very good SDC and can double for a vocal mic if you use a pop filter, and that's not strictly needed if you sing off-axis a bit.
https://www.sweetwater.com/store/det...ser-microphone