This conversion seems to be mainly representing an export of maps or other images saved in LizardTech MrSID format (.sid) to some common picture format like PNG. It can be done with some dedicated conversion utility, but be prepared that the resulting files may be very large.
Convert LizardTech MrSID image file format to Portable Network Graphic.
We have found 2 software records in our database eligible for .sid to .png file format conversion.
Microsoft Windows software - convert sid to png on Windows
A dedicated converter for SID format
Convert from sid file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned sid to png. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A converter that is able to transform various GIS file formats