Hi Sue,
Here's the Toshiba manual for your VCR.
[link|https://data2.manualslib.com/pdf2/38/3743/374288-toshiba/m683.pdf?91a74d58bea7c8d14ac64174a7aa3c44|TOSHIBA M-683 OWNER'S MANUAL Pdf Download|new_window=true]
The manual doesn't mention any buttons specifically labelled "Mode", but there are a couple of different references to the word "mode", such as setting it to either TV or VCR mode. What is it you're trying to accomplish with the "Mode" button that you're looking for?