As described in this post in external forum, CODESYS v35 (32-bit) does support a v23-to-v35 conversion tool. (See answer from aliazzz.) If you have the original .pro file, maybe this would be a potential workaround.
Since ctrlX PLC Engineering is based on the 64-bit version of CODESYS, direct support for .pro conversion (or for importing the associated .exp file) seems unlikely.
The conversion tool is described here: https://store.codesys.com/de/codesys-v2-3-converter.html
Note that 64-bit support is explicitly excluded.
