You can compose compose conditional or hypothetical phrases using 〜たら. You can compose it using the plain past conjugation of a word and appending ら to it. This is one of many ways of forming conditionals or hypotheticals!
- noun + だったら
- i-adjective without final い + かったら
- na-adjective + だったら
- verb plain past + ら
Use もし to begin the sentence to make the meaning more of an if, and leave it off to make it more of a when, though I'm not sure of this yet. It usually seems right to omit it.
- Literal: If it were me, I'd look for a new apartment.
- Natural: I would look for a new apartment.
- Literal: If you eat this mushroom, you will become taller.
- Natural: Eating this mushroom will make you taller.
Maggie Sensei has a much more complete article on たら.