Since no info on your converter box comes up in searching here is some general information.
You can use a universal remote but there are different kinds that program differently.
The cheapest and most common type has a number of codes for different makers and models of devices. To use this type with your box you have to make sure it has a 3 or 4 digit number that accesses the codes stored on the remote for your converter. Check the remote makers website or contact them to confirm that the correct codes are present on the remote. Sometimes they have the codes but not in the remote and they can program them on to one for you. Sometimes they don't have them and you can't use their remote.
The second type adds a learning function to the first type. To use this you need access to an original remote so you can teach each button onto the universal remote. This can be tricky depending on the remote and you would need to borrow the original one.
The third type is programmed over the web (Logitech Harmony remotes) or with a PC (URC or RTI). These are also learning remotes but have a large database of codes from the maker and users. More expensive.
If you can contact the maker of the box it would probably be cheaper to buy a replacement remote.