migrate version 1.5.2.1 to 1.5.4

I try to migrate version 1.5.2.1(old) to 1.5.4 (new) The problem when i restore all the files is " Warning: The file you uploaded was empty!" How can i fix this issue ? I have almost 3,000 products online and it is time consuming if i do it again manually it will cost time .

There is a service which can help you out. It offers automatic data transfer, and it's not time consuming because it will move your 3000 products in an hour or two...(well, depends, but it worked for me that way)
and you will not bother about lost data or duplication as it might happen when you transfer manually. so I recommend you to take a look http://www.shopping-cart-migration.com/ ... 7-opencart
+ you may even register and try it for free here https://app.shopping-cart-migration.com/#register
I guess it's better than to hire someone to make the work for you - at least here you see immediate results and know what you are paying for