Hi, Is there a quick formula for calculating an approximate figure for the quantity of lumber required to frame a given space (in my case, my basement)? Thanks

I have a house that was built in the 1740s. The 6x8x16 that supports the attic floor is sagging. The floor joists are mortise and tennon and pegged on 24” centers. The beam is not cracked. My idea is to lift the sagging beam back to level, support the ceiling with 2 temporary walls (the temporary walls will be 2 2x8s screwed together and supported by screw jack poles 4’ on center. Is this over kill or inadequate? ) then cut out the floor joists. Then sister an lvl beam to each side of the 6x8, through bolt the lvls and use joist hangers to reattach the joists. My questions are how wide lvl or how many lvls should I use in the 6” space I have between the second floor ceiling and the attic floor. Or because of the 6” limit should I consider steel plate? And if so how thick? A ½ inch plate on both sides? Lag bolts to the original beam? Lag bolts instead of through bolts because drilling accurately through all that would be difficult to say the least. Thanks in advance!!