Assuming you have a unique Ubuntu home partition:
1. In the installation, select the "manual partition" option (or verbage close to that)
2. Identify the partitions that you want mounted in your new Mint ops.
2a. Select the partition where Ubuntu Home lives.
2b. Edit the partition
2c. In the mount input put something like "/media/UbuntuHome"
2d. Continue identifying the other partitions that you want mounted at time of booting Mint
3. Carefully verify your entries
Hope this helps.
Linux'd since 2005 Linux ID 422356 Ubuntu ID 15015