Sharepoint / Azure Storage Best Practices

Hello -

We are buying a company and beginning to look at bringing all resources in.  2 old systems they have will be replaced with what we are currently using, leaving around 5 TBs of data that will need to be queried every 3-6 months or so.  We do have hardware on prem where we could just throw it on there and save on costs but Sharepoint or Azure may be best if the cost is not too high.

Our current Sharepoint library has all company documents and we have 2 TBs free of 4 TB.  So I guess that isn't the best option.  Next would be Azure?  Azure cold or archived?  I am not too familiar with that.  In the end, we want to have this data accessible whenever it would be needed (compliance or audits, for example) but do not want to spend a ton.  If on prem is the best option, we are OK with that too.