Missing funds

So about 5 years ago I used to be buying and selling on Binance with about £500 within the account but I ended using the account as truthfully I didn’t have a clue what I was doing and didn’t have the time. I might perhaps each 8-10 months log in and all the time see that I used to be nonetheless round £500 in a coin referred to as NULS. But right now I logged again in as a result of I deliberate on withdrawing the money as it was pointless having it in there to seek out that I’ve solely acquired $11 in USDC. I checked my emails and that i acquired an e mail saying 1518.54 NULS has been transformed to 11.44 USDC. What has happened for £500 in a coin been converted to $11 and is there something I can do? Did the coin utterly crash? Any advice is enormously appreciated, thank you!