I am trying to migrate Sitecore 7.2 instance to Sitecore 9.1 using Express Migration tool which are on remote servers. Here is the screenshot of inputs. Is this the right way to provide inputs or I have to host names in website folder.
Assuming that you are using Express Migration Tool 3.1, From Express migration tool installation guide, https://dev.sitecore.net/~/media/4B49AAB1EBE94F55ADF07A7740AABBC8.ashx
When referring this KB https://kb.sitecore.net/articles/400952 looks like none of the version supports to migrate directly to 9.1 from 7.2.
The Sitecore Express Migration Tool 3.1 is designed to help you migrate directly from older versions of Sitecore to the latest version of Sitecore Experience Platform™ 9.0 rev. 171002 (Initial Release).
It may not work as expected, when you set your target instance as Sitecore 9.1. So it would be better migrating to 9.0 and then migrate to 9.1 using the migration steps https://dev.sitecore.net/~/media/E78AB08CE53F4C27B668A6D49791C9D3.ashx
And for the website folder always noticed, if the Website folder [whatever given in the parameters] is accessible [read/write] from the device where we run the migration, I think that should be enough.