Port LTM and GTM configuration from v10 to v11

I would upgrade your old appliance to the same version you are migrating to, that why you can validate the code and make sure your application still work. Then use an SCF to restore the configuration to the new device:

https://support.f5.com/kb/en-us/solutions/public/13000/400/sol13408.html

What are you upgrading from and to? You may have differences such as interface names, so you could always do this manually or merge a new bigip_base.conf file. The bigip.conf file contains config which is appliance independent so you could always copy a version of this over from the old appliance to the tmp folder and run the following:

tmsh load sys config file /var/tmp/bigip.conf-from-old-appliance merge verify

the 'verify' syntax doesn't load the config, just makes sure it's valid. Once you're happy you can omit that part of the command to load the new config

Rough Guideline:

1. Backup the configuration on the device and if possible in another location.
2. Depending on your support contract, you may be able to open up a pro-active ticket for code upgrade support.
3. Make sure that your box's license date is compliant : License Check
4. Save the UCS configuration (old_config.ucs) for the 10.x LTM. Copy it over to the new appliance with 11.x.
5. Execute the following: tmsh load sys ucs old_config.ucs no-license no-platform-check

I am making an assumption that you have already checked the license check date, no ip/route is changing between the 2 models of devices. Keep the new device ports shut to prevent any network conflict.