Although both .flka and .flk files originate from Folder Lock and are used for encrypted files or archives, it doesn't seem possible to convert one to another. At best you could decrypt the files and get the original contents back and then encrypt again with a different function, but that's hardly a conversion.
Convert Folder Lock encrypted portable folder file to Folder Lock encrypted file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert flka to flk on Windows
A data security program
Convert from flka file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.