List Migration Option 
1. The List Migration Optiondialog will appears as shown below:

2.

Select anyone of the following options given below to specify the content to be migrated from the source sites:

  1. Merge list contents - This option merge the list contents only with the following options
  2. Replace list, if it already exists- This option replaces the list in the target location, if the list already exists in the target location.