Audio file for how to say “welcome” in Japanese
ようこそいらっしゃいました(youkoso Irashai mashita)
You may wonder what is the difference between ようこそ(youkoso) andいらっしゃい (irasshai) since they are used in the same sentence
Most likely ようこそいらっしゃいwas broken up and evolved into current form.
いらっしゃい=It can also mean come over here
Thus linking the two becomes something like “Welcome to come over here” (Welcome to come all the way to our place)
Check out this post about いらっしゃい