Verifying DOB/F stated Building Square Footage

I checked on this link but it does not have the building in Manhattan I am interested in.
https://nyre.cul.columbia.edu/

That's an interesting website. Have you tried:

www1.nyc.gov/site/buildings/index.page

Yale Robbins was always the go to for this information. But I see the Columbia U. site has YR so it may be hard to find. Could check with REBNY library.

Thank Ximon. I know the website but it does not have floor plans - at least I have not been able to find them.

No, you won't find floor plans there. If you know the building manager or super, you could ask if they have the floor plans. I have found some interesting documents in a super's or manager's office.

Assuming this is a condo or coop, the offering plan. There are several sites that have a large number available for free. Condo offering plans can often be found on ACRIS

Offering plans are (or were) also available for inspection at the NYS Attorney General's office.

Thanks. Unfortunately, I am looking for commercial / rental building floor plan. It looks like, you just have to ask the seller.

For commercial space, we used to use costar but that's a paid service.

I know. Costar is very expensive unfortunately.