OBD1 plug does not Fit how can I retrieve engine codes

You need either a tech 1 or tech 2, I forget you have an obd1.5 which GM used for one year only it probably has a fourteen pin connector. You can try jumping A and B with a paper clip or jumper wire and turn ignition on and count flashes of check engine light then get back to us with the codes. Three flashes once mean one and so on so you get a two code number twelve is normal.

Welcome to no mans land. You have the lovely OBD 1.5! It uses the OBDII style DLC, but is not OBDII compliant.

There may be a way to get it to flash the codes on the Check Engine Light.

Look at the picture and your connector. It should look like the bottom one (may be mounted upside down so look at the mounting ears.)
If you have pin six (some do some do not) You can connect pins five and six. Turn the key on, not start. Then count the flashes that the check engine light does. It should flash DTC code twelve three times. This would be the following flash sequence: "flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash."

DTC 12 indicates that the diagnostic system is operating. Any codes will flash the same way, and repeat three times, then it will cycle back to code twelve indicating that you have seen all the codes.

The bottom of this page lists most of the codes.
https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

The ABS is a different ball of wax. There are ways to make the ABS light flash the codes on the older OBDI systems but not on the OBDII units.

An older OTC Genisys with the ABS software can handle both jobs. But you have to have the older cable that used keys not the smart cable.

You could probably find a older mac taskmaster or old otc nemisys that should read the ABS and engine computer. They have them on eBay for sale. Sometimes with the older years software on them you can pick them up for a great deal.