Auto Naming

I am working in a table where, for example, column B is "Job Number", Column C is "Order Date" and Column D is "Vendor".  I want to populate Column E automatically with the purchase order number which is "ColumnB"_"ColumnC"_"ColumnD".  To illustrate:

B5 = 7556 (text)

C5 = 09/08/2018 (needs to convert to 090818 format)

D5 = Springfield Electric, Inc. (needs to convert to the abbreviation SF)

I want E5 to auto populate with: 7556_090818_SF which is how we number our purchase orders.  I think I can get the date to convert (although don't hold me to that, advise is appreciated) and I probably need to define the abbreviations but how do I get E5 to populate with that information?

I have attached the template...it is still a work in progress so please no judgement.