Question

how did thor know that he had to arrive in wakanda after getting his axe

Answer 1

cause he is the god of thunder so he had where to come

Answer 2

After the events of Ragnarok, Thor is now the All-Father. He is capable of many feats that have not been shown on screen yet, which Thor begins to unlock when he wields Stormbreaker(a kings weapon). This is what allows him to open the bifrost, and it is certainly within the realm of possibilities that the awakening and development of his new powers includes some form of Odinsight, which the All-Fathers past have used to watch over the 9 realms. He could have used the Odinsight to see the events unfolding on earth and decide where to go.