These small metal discs cover holes in the engine block and can corrode or simply fall out over time, especially on older engines. You can't drive your car like this, as it will quickly overheat. You'll need to clean the bore thoroughly, get a new metal freeze plug of the correct size (brass is often preferred for corrosion resistance), and install it securely with a hammer and a suitable driver. Using a thin layer of sealant can help ensure a leak-free fit. Once installed, refill your cooling system with a proper 50/50 coolant mix and check for leaks login on Prepaidcardstatus

https://www.minimania.com/part/CP8-EA%2E/Convex-Core-Freeze-Plug-848-948-998-1098cc-A-series-Blocks

No. it was brass rod and I had to  cut to fit the freeze plug hole..

like this?

Uxcell Copper End Cap Pipe Fitting Sweat Plug Connection for Pipe Plumbing 38mm - Walmart.com

Last time I had to install.. I just went to lowes and got proper copper plug.. and hammered in it.. I forgot the size.. 

It appears that I lost the far right front freeze plug on what I think is a 1098cc engine

Was going through checking everything for next weekends british field days in Sussex and notice low fluid in the radiator.  Put in some water and out the water went.

     other freeze plugs look like this

which one do I need to purchase to replace it and any helpful advice

Freeze Plugs S Each , Steel Mini Cooper S

or

Convex Core Freeze Plug, 848, 948, 998, 1098cc A-s

found this 

replacing_a_freeze_plug

Thanks for the help!