"Hundred and one" is the number 101. "Hundred and one other jobs" means there are 101 more jobs than another one (which was probably mentioned in an earlier sentence). The sentence is not entirely correct, because it is incomplete.

The sentence "Doing the hundred and one other jobs which are needed in a garden." is not correct. You would write "I need to do a hundred and one jobs in the garden." The idiom is "a hundred and one". When you say it, you pronounce the "a" as "uh" rather than the long "a" sound. This idiom means "lots" or "many". An example of it's use in a sentence would be: "I've got a hundred and one things to do today." This idiom is not used very often in spoken english, though everyone would understand it. A similar idiom that most people use is: "a thousand" An example of it's use in a sentence would be: "I've got a thousand things to do today."