iPhone passcode not known

[hadwebutworldenoughandtime]

My father died recently and my mum needs to access his contacts on his phone to let some of his friends know. I thought i had written down his 6 digit passcode down but it's not right. Prob off by only one digit or order of digits ax it forms a logical pattern.

Is there any way to get it unlocked without deleting everything? Don't think it's backed up but don't have Apple ID password -although can access his email so this could poss be reset.

Also I have tried various combinations but lock time gets longer each time- how long before I am locked out for good?

Thanks

Could the logical pattern be related to a birthday/football team big win or something? Just that’s what people normally use

Thanks LouiseTrees I've managed to get in and change it now and still no idea of the logic! But I appreciate your reply.