Run your plasmid on the gel and cut the right band, then do sequencing to confirm it. You can do a normal PCR for the purified band also.

I agree with the two previous suggeestions. In addition, due to its length, at such a high concentration, genomic DNA should be highly viscous, much more so than plasmid DNA

You can verify it on gel after digesting with unique enzyme that will linearize your plasmid,  if it is genomic DNA you will get a smear  otherwise you get a single band of the expected size of your plasmid.   if the concentration is correct, your preparation should bi viscous.