Sharp pos terminal up 3301

A couple of ways you can transfer between till. Either use software like posutility to take a ram image of the working till, or buy/make an APLD cable to transfer data between tills. The 3301s don't have an infra red data transfer connection like the 3300s did unfortunately.
You don't mention whether these machines were connected together as Master and Terminal or were stand alone.

They are both connected via Ethernet cable. And they both have infrared ports on the side of them next to a small switch. They're are options along the lines of send data and receive data. I am not sure which is master a slave

If the working machine is not giving any errors and is working fine then that's probably the master machine.
Sharp were lazy with the 3301s. It looks like the IR port is there from the outside, but there's nothing on the inside.
I've not got a wiring diagram handy at the moment, but when I do I can put up the pin outs for the APLD cable (it's on this forum somewhere too). If you're not too good at making cables, google Sharp apld cable and you should find one. If you're ok with setting up a static IP address on your pc, then you could use PosUtility to upload a copy of the working one to send to the non-working one.
Before any of that though, have you any idea why the one machine became corrupted? My guess would be the back up battery is at the end of it's life and the machine was unplugged. They're easily replacable though. It's just a cordless phone battery that you can pick up at Maplin etc.

APLD cable is as Jacky-s put on the 307 post. Which if you don't know what that means is:

9 Pin Female D type 9 Pin Female D type

1-4-6 1-4-6

2--------------------3

3--------------------2

5--------------------5

7-8 7-8