ZIP archive of about 5.58 MB whose name, LB35B, gives little away; it may be a board or project code, but the device, brand and contents are not stated. Open it and check what it holds, whether schematic, boardview or firmware, before using it. Compare any board number found inside with the marking on the PCB. For firmware dumps, back up the original chip with a programmer before writing and check that the image size matches the flash capacity.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @gunvantrathore. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.
Built-in OS tools7-Zip