Laura you need an interface with multiple inputs. I have a onyx black jack by Mackie

https://mackie.com/products/onyx-blackjack

It is no longer made but the update is and is good kit well priced. They have 2 channels like the popular Focusrite scarlet

https://focusrite.com/en/usb-audio-interface/scarlett/scarlett-2i2.

Depending on your set up you may need one of these channels for your guitar other wise if it is just two microphones then this these will answer your cause. Your guitar amp such as the THR10C and most new amps may output an electric guitar to USB directly but if you are not able to make that link then you need more inputs to the interface if its an electric guitar and two mic you need. Bigger versions with more inputs cost more. I don’t know if it is possible to set up two, two inputs units via USB to get 4 into a DAW I would think it quite likely but have no knowledge on that but I am sure someone here will help.
JohnStrat

Laura, you will need a mic mixer, these are multiple input mic sockets, they come in sets of 2 to 8 afaik. Prices vary from about £20 to a few hundred, i dont know if a mic cable splitter does the same job or not. Im sure someone will pitch in soon to let us know for definite..

Sooner or later you will need a Focusrite Scarlett 2i2 anyway, so why not just buy one now? Each of the two sockets will accept either a mic plug or a guitar plug. They get their power from the USB connection to your computer, but if you don’t want to plug it into your computer, just plug it into any USB power source. And if you want to feed it into your amp rather than a computer, just feed one of the 2i2’s monitor outputs into your amp. Voila!

Laura I should have put up the link to the replacement unit for the BlackJack I believe it has had reviews up rating to the Focusrite and I know it is competitively priced. I will see if I can spot the review but they area all very similar and I don’t think we are likely to know the difference. I can say that Mackie is extremely toughly built resembling a military type specification and that they have been around in the professional recording world for a long time.
JohnStrat

https://mackie.com/products/onyx-usb-interfaces-1

Hi Laura this might explain the splitter Billy talked about, more info on the the interface the DAW and what you are trying to achieve would have helped.

Vorocnan

And here is a review which favors the Mackie Onyx and I believe it now does come with a bundled DAW or some sort of software Avid.. Pro Tools First, Traction or Waveform not sure but it would become apparent at point of purchase.
Hope that helps.
JohnStrat

Laura There is yet another point and that is that if you acquire a unit that has a MIDI port which the new Onyx has and you wanted to piggy back another such unit I think MIDI might make it possible but it would be a question to put to Mackie or Focusrite etc. Also be aware of the bigger units like the Big Knob by Mackie (note, it also only has two phantom voltage mic inputs.)

There are various solutions as already mentioned. What type of mics are you using? Also what ever you get need to make sure your daw is compatible. I like the Focusrite but you may consider more inputs so you can expand later need to mic voice and more than 1 instrument.