how are old books, scrolls, & parchment paper conserved for museums?

Answer 1

well it depends what you mean by conserved - they are stored in appropriate materials, acid free paper boxes, polyester sleeves etc.
But the meaning of conserve is huge - it ranges from cleaning to manual repair - so you need to be more specific

Answer 2

It depends upon how old the artifact in question is and how it was stored in the past. Some are kept in anhydrous conditions (that is to say in humidity controlled tanks to stop water in the water vapours in the air causing decay). Others are kept in water, or oil or another liquid to stop dessication. Some are laminated, some are impregnated with a clear plastic resin to stop decay. Some are sandwiched between glass sheets.
Most are only allowed to be handled by museum staff to prevent damage and usually this involves special gloves to stop oils and acids from the skin causing damage. Some have scanned copies available for museum goes to read.