This is the beginning of an indirect quote. It can also be translated with a direct quote, as in the UDB. (See: [[rc://en/ta/man/jit/figs-quotations]])
The phrase "must be" means this is something that would certainly happen because God had already decided that it would happen. This can be translated in active form. Alternate translation: "it was necessary that they hand the Son of Man over to sinful men who would crucify him" (See: [[rc://en/ta/man/jit/figs-activepassive]])
The Jews counted any portion of a day as a day. Therefore, the day Jesus was raised was the "third day" because it followed the day of his burial and the Sabbath day. (See: [[rc://en/ta/man/jit/translate-ordinal]])