。
Without taking risks, you won't get anything.
Literal
Adventure [object-を] don't-do-if, nothing not-get.
手に入る ('to come into one's hand') is the everyday Japanese way to say 'to obtain, to get hold of.' It's intransitive — the thing obtained is the grammatical subject (elided here), and the human acquirer fades into the background. The transitive counterpart is 手に入れる. The proverbial frame 冒険しなければ何も手に入らない echoes the English 'nothing ventured, nothing gained.'