I suspect you will have to open the files in Lotus 123, then save them to the .xlr format. In much the same way that you can do it to open a file created as "abc.123" (in Lotus 123)in Excel (Office) as "abc.xls".
Or if you look at the 'save as' in 123 you should find a choice of file types to save in, including Excell types, which are I believe .xls. It should then open in the Works spread sheet if you choose the XL option for the type of file to find, however you may find that some figures, if formatted in 123 don't come out right!
Unfortunately I don't have Excel and I don't now have access to a PC with Lotus. I transferred the files in question en bloc when a friend replaced her PC and I evidently did not anticipate the problem in advance. There were too many other things to think about at the time.