Prostores products data, cms page and customer data can easily moved to bigcommerce. It can be done using very intuitive csv import function provided by bigcommerce.
We have recently helped several prostores owners to migrate to bigcommerce very smoothly. We try to make the process as smooth as possible. We also create setup so that you have to loose any of the seo work done already. We use seo redirects to give you same url structure so that pages still rank well with google.
If you have a prostore setup and you wish to move to bigcommece but not sure how the process will flow. Please feel free to call us on toll free number 1-8663553113 or mail us at firstname.lastname@example.org