The command above generates 100 additional addresses. This assumes that you have generated and used at least 100 additional addresses from the 2017 to the current day. You can increase the integer as necessary

That has fixed it 

Your legendary status is well earned! Thanks ever so much for your help

Thanks for all of the replies although I don't understand the latter ones unfortunately.

The address I sent the bitcoin to begins with a 1.

I followed OmegaStarScreams instructions 1 (thanks a lot - much appreciated). My electron cash wallet shows I have some BCH. I also had some bitcoin in Electrum.

Does the Electron Cash wallet include the bitcoin I had in Electrum? If so how do I distinguish between the bitcoin and bitcoin cash? When I went to get a receiving address from coinbase it warned me if I send the wrong currency to it, it will be lost forever.

Also the dates for the transactions shown in Electron cash are from 2017 not 2021 and they don't seem to correlate with the amount I sent. I sent 0.77 bitcoin cash and the balance showing is 0.00489243 BCH, which appears more like a bitcoin balance to my uneducated eye. I am certainly not aware of it but is it possible that I have put the wrong seed in and this is showing me and old wallet I did not know/remember I had with bitcoin in?

Thanks a lot

I purchased bitcoin cash by mistake thinking I had purchased bitcoins (when slightly inebriated) and sent it to my Electrum wallet. It shows the transaction as unpaid in electrum. I did some research on here and I understand that I need a different wallet that can accept bitcoin cash. I have downloaded electron cash but I don't know what to do next. Can someone please in very simple instructions help me to set up bitcoin cash and recover the money so that I can send it back to my coin base account. Sorry I am out of my depth here. Thanks a lot in advance