where'd you got that xprv key?
Normally, that xprv can only be exported when you click on the Bitcoin HD account -> menu -> Export account keys.
And that's the "BIP32 Root key" for that Bitcoin account's addresses that starts with '1'.
If you did exactly that ^ , then that backup if for your Bitcoin account with legacy addresses,
not for Ethereum, Bitcoin Native SegWit nor Bitcoin P2SH-SegWit.
You need Mycelium's "Master Seed" (12-word phrase) to restore the wallet completely.