Hi @RSaraiva,
Each company should have its own HubSpot account or alternatively if you have your own Enterprise account and business units, you could have the leads in one account with some separation.
Who ultimately owns the data? If the lead data is to be owned by the individual companies, I would go with 3 separate portals.
Technically you could do this in one portal without Enterprise, but it is not advised.
Hope this puts you on the right track!