וְיוֹסֵף֙ בֶּן־שְׁלֹשִׁ֣ים שָׁנָ֔ה בְּעָמְד֕וֹ לִפְנֵ֖י פַּרְעֹ֣ה מֶֽלֶךְ־מִצְרָ֑יִם וַיֵּצֵ֤א יוֹסֵף֙ מִלִּפְנֵ֣י פַרְעֹ֔ה וַֽיַּעְבֹ֖ר בְּכָל־אֶ֥רֶץ מִצְרָֽיִם׃
Joseph war dreißig Jahre alt, als er vor Pharao, dem König von Ägypten, stand. Und Joseph ging von Pharao hinweg und durchzog das ganze Land Ägypten.
Rashbam on Genesis
בן שלושים, and old enough to assume the burden of high office.
Sforno on Genesis
ויעבר בכל ארץ מצרים. In order to supervise the storage facilities in the cities and to organize matters. We find the prophet Samuel as traveling the length and breadth of the country instead of waiting for the people to come to him in Samuel I 7,16, וסבב בית אל...והמצפה, “and he made the rounds (annually), starting at Bet El and finishing at Mitzpah, his home.”
Or HaChaim on Genesis
ויעבור בכל ארץ מצרים, he traversed the whole land of Egypt. This was in order to familiarise himself with all the fields, to gather information about where to establish silos, etc.