Migrating older F5 BIG-IP has 3 partitions & Route Domains (RD) to new F5 BIG-IP with 2 partion & RD

Hi mmsuwaid ,

1st Method
===========

1. you need to identify Partition specific configuration files which are loacated in /config/partitions/<name>/bigip*.conf

Once you finish the procedure use
load sys config verify

Your UCS Should simply be an archive.
Try zipping it up with winzip/winrar and changing the file extension to .ucs. after removing/editing the desired partiton files residing in /config/partitions/<name>/bigip*.conf

Once done you can zip/pack your UCS file back and give it a file extension .ucs.

2nd Method
===========
I extensively use
load sys config merge from-terminal

Very helpful command for Enter configuration.

Press CTRL-D to submit or CTRL-C to cancel

Prerequisites

You must meet the following prerequisite to use this procedure:

You have Advanced Shell (bash) access to the BIG-IP system.
You are proficient with basic Linux commands.

Procedures

Extracting the UCS archive to a temporary directory
Deleting all unnecessary large files from the UCS archive
Repacking the UCS archive
Installing the new UCS archive

https://support.f5.com/csp/article/K12278
https://support.f5.com/csp/article/K13830181

References for load /sys config merge from-terminal with sample examples

https://support.f5.com/csp/article/K81271448
https://www.xglobe.com/knowledgebase/networking/f5-load-balancer/f5-copy-ltm-config-to-another-device/

"load sys config merge "  with the help of an example

You can use the load sys config merge command to import the configuration as written in bigip.conf. 

If you want to write to a particular partiton change your folder using 

cd /Partition1

or 

cd /Partiton2

and then use the load sys config merge command so that the configuration will be written  in bigip.conf file for that specific partition or else you have to give in the name reference like we give 

/Common/VIP1 

......

/partition1/VIP10

/Partition2/VIP20

First, enter the load sys config merge from-terminal command.

Create a text file like the one below and paste it into the terminal.

Ctrl+D reflects the settings, and Ctrl+C cancels the operation.

Let me know for any further help.

HTH