our band practices on mondays at josefs, thursdays at lenas and saturdays at my house
the first one
Our band practices on Mondays at Josef's,Thursdays at Lena's,and Saturdays at my house.
The correct sentence is "Our band practices on Mondays at Josef’s, Thursdays at Lena’s, and Saturdays at my house."
The times and places where the band practices need to be separated from one another to avoid confusion. For this we can simply use a comma. We would only use a semicolon to separate the items if the different items also included commas. For example, "The different plants include a plant with yellow, white, and pink flowers; a plant with blue, purple, and pink flowers; and a plant with red, white, and yellow flowers. Here, the semicolon separates the different plants to avoid confusion. Also remember that a colon should only be used after a complete sentence.