1. Check the Private Key Format:
Please read the entire thread first.
And he already answered that in this quote:
Yes it does start with 5
-snip-
4. Choose "Use a master key".
5. Instead of a seed phrase, paste your WIF private key (starting with 5).
This is wrong, uncompressed WIF isn't a master (
extended) private key and will not be accepted in that menu.
Electrum will NOT sweep uncompressed keys but will accept them in wallet creation.
Wrong again, it accepts uncompressed and compressed WIF in both Import (
wallet creation) and Sweep.