The most reliable way for this conversion would be to use Lotus 1-2-3 spreadsheet editing software to save .123 spreadsheet file to another version of Lotus spreadsheets, for example .wk1 files. However, Lotus 1-2-3 is legacy software that was available for MS-DOS, Windows and Mac OS Classic so it may be pretty hard to make it work on modern computers.
Some modern programs like Libre Office Calc supposedly support both of these file types and should allow users to perform this conversion.