way to import few orders/user after upgrade to D7

Personally, if it's only a few orders, I would do it manually. On your new site, set the initial order number to be equal to the current order number on the old site PLUS a large enough offset that you won't have to worry about duplicate order numbers (see the FAQ for how to set the initial order number), then when the new site is ready to deploy, you only have to manually copy those few orders over. Any orders placed on the new site will have order numbers > the old site, so there will be no overlap (but there will be a gap of unused order numbers).

You can just manually dump the table rows that refer to the few orders - part of your development on the new site will be to create an appropriate query to dump all the rows that contain order information for those few rows, so when you're ready to switch over you just have to put the old site in maintenance mode, then dump from the old site and load to the new site - shouldn't take more than a few minutes, and your new site will be online the whole time so you won't miss any orders.