How to create pop up with for example customer name?

I have a large document which has about 150 times the customer name in it and multiple other items which I need to update every time I create the document for another customer.

I remember from a long time ago there used to be Word documents where you would get a popup, fill in some information and it would fill this out through the whole document. I would like to create this for my document, but working on it now for a day has left me with nothing much.... who can help?

Thanks!

p.s. I use Word 2016 for Mac

ctl-H (is find/replace)

it will ask you for the existing word,
and the replacement word
then click REPLACE ALL

Yes thanks, that is the method I use right now, I am looking for something better as there are about 15 of these items that need to be filled in. I want a better way to do this...