It all depends on the type of files exported/saved from Proventure and the type of files that MyInvoices & Estimates Deluxe allows importing. You have to open MyInvoices & Estimates Deluxe and access the Import function. It can be a simple File > Open or through a different menu like File > Import and then make certain adjustments.
The problem is that MyInvoices & Estimates Deluxe developers don't specify what are the exact file types you can add into the application which means you can either test by yourself or contact them and ask for this info.