"四坏球自由上垒" can be translated into English as "base on balls (or walk), allowing the batter to advance to first base automatically".
However, for a more concise and commonly used expression in baseball terminology, it is often simply referred to as a "walk", with the understanding that a walk entitles the batter to advance to first base without being put out. If you specifically want to emphasize the aspect of "free advancement to first base" due to four balls, you could say:
"A walk (or base on balls) grants the batter free passage to first base."
But in most casual or even professional baseball discussions, just saying "walk" is sufficient to convey the meaning of the batter advancing to first base after receiving four balls.