Hi @Goose05,
You could refer to screenshot below to create the flow to move file from library1 to library2 when the file is older than 30 days:


The expression in the Condition as below:
@lessOrEquals(items('Apply_to_each')?['Modified'], addDays(utcNow(), -30))
If you want to move file from library1 to library2 when the file is older than 3 years, the expression should as below:
@lessOrEquals(items('Apply_to_each')?['Modified'], subtractFromTime(utcNow(), 3, 'Year'))
Best regards,
Alice