There is not a particular word for relative pronouns in Chinese. What we do is to put the description before the thing being described, and link them together with 的 (de.)
Your sentence can be translated into:
那个刚走进店里的男的很高。
Let's build the sentence together:
"男的" (man)
"刚走进店里" (just walked in to the shop)
"刚走进店里" (just walked in to the shop) is a description of "男的" (man.) Therefore, let's link them together with 的:
“刚走进店里的男的" (a man who just walked in to the shop)
Since he is not a random man, but a particular one, let's add "那个" (that) to the sentence:
"那个刚走进店里的男的" (the man who just walked in to the shop)
Finally, this particular man is tall. Le't add "很高" (very tall) as the predicate of our sentence:
"那个刚走进店里的男的很高。" (The man who just walked into the shop was tall.)
Hope that helps!