Hi, and welcome to ITKE.
I will try to help, but without seeing the actual config, this is a bit of an impossible question to answer with any real accuracy. I don’t think it would be a good idea to post the configs here either.
Generally, you need to take the parts of the config, from both devices, that have different commands, and put them into a single config. Items that have the same command, but different values, such as IP addresses, you will need to take a decision on which one is the one to keep. First make sure you have taken backups of the configurations of both devices, so you can revert if necessary.
My advice would be that this is one occasion where you need to get an experienced person to work on the actual configurations. They will be able to ask detailed questions, based on the different configuration items, and give you a fully working end configuration, that works on a single appliance.