If you were wondering if you can use your existing Jam+ (Jam Plus, Jam, Jam 96K) to record voice, acoustic guitar, etc. using a microphone, then the answer is yes.
While Jam+ does not have an XLR input connector, you can use an XLR to 1/4" impedance transformer (an adapter) to connect any dynamic mic or ribbon mic to Jam+.
A Line-matching Transformer is an adapter with a female XLR connector on one end and a male 1/4” connector on the other. This transformer converts the low-impedance signal of a microphone to high-impedance for connecting to a device like JAM. In this process, the transformer is providing additional gain for optimal signal level.
Note: A condenser mic may not be used since Jam+ does not supply phantom power.
Here's a video of singer-songwriter Joel Taylor using Jam+ to record guitar, bass, and voice for his song "Two Sides":
You can buy this exact adapter from here: https://apogeedigital.com/shop/mono-adapter-jam