I ended up working it out myself.

In MemcardRex under Edit >> Import save, this uploaded the game file.
Then once I clicked on the game file again under Edit I Export save to an mcs file.

The mcs has to then be converted to an mcr file which I did using this website http://www.save-editor.com/tools/wse_ps1_save_converter.html

Then just renamed the mcs file to be an srm as per this guide https://recalbox.gitbook.io/tutorials/playstation-1-psx/convert-.gme-save-game-psx-to-.srm-save-game-for-retroarch.

I am stoked to have got it to work and hopegulyl if anyone stumbles across this it may help.