[Marco Villar]

Yes, just export the file as an INX file, if I’m not mistake you should then be able to open it in CS3. That was the procedure for converting from CS3 to CS2 anyway.

[Marco Villar]

Don’t know if you’re still looking for an answer, but there are two ways of doing this. First you can use a script, InDesign comes with a number of built in scripts, including one that can export text. I think where it is varies by what version you’re using. However if you plan to import the text after translating it I would not recommend this option since there is no free import script. Your other option would be to use a CAT Tool, there is a guide to using one to do this here:

https://heightstranslators.com/translating_adobe_frameMaker_and_indesign_files_in_across/translating_adobe_frameMaker_and_indesign_files_in_across.html

Beware, you will probably need to adjust the text a little after reimporting, and if you’re not using Across the general procedure remains the same from the InDesign point of view, save it as instructed.