expression
if possible; if it can be realized
A set phrase expressing a wish or hypothetical condition, often used when the speaker hopes for something that may be difficult to achieve. Literally 'if it can come true'.
叶うことなら、もう一度彼に会いたい。
If possible, I'd like to see him one more time.
叶うことなら、来年は海外で働きたい。
If it can be realized, I want to work abroad next year.
From 叶う (to come true, to be realized) + こと (nominalizer) + なら (conditional of だ). The phrase literally means 'if it is something that comes true'.