If you need to produce files in Open Financial Exchange format (.ofx) from data exported in plain text format (.txt), you have to download and use utilities, such as csv2ofx that allows users to process various text formats and produce OFX formats. This probably only works for formatted text files that contain relevant data and not just random ones.
Convert Simple text file to Open Financial Exchange format.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert txt to ofx on Windows
A converter for bank and credit card files
Convert from txt 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.