Mandarin equivalent for 返嚟? In Cantonese 返嚟 is often used when asking someone about where they obtained something from. For instance, "學返嚟“ could be used in a sentence asking someone, "Where did you learn this from?"

What's the Mandarin equivalent for 返嚟 in this context?
The most usual verbal suffix is just 來/来 lái. This can be combined with 著/着 zhe after it. See Definition 7 here:


  7 用在动词后，表示做过（一般均可用“来着”）：昨天他哭～。


The use of 来着 is very frequent in northern colloquial Mandarin, but is a more general past tense marker with some sense of "just now", with an idea of a continuous state according to some analyses. It is a very well researched construction in academic studies of Mandarin.

The most common equivalent for Cantonese 返嚟 is Mandarin 回來/来 huílai, but this is more restricted in usage as a verbal suffix, and has a stronger connotation of "coming back home" (e.g. buying something back, receiving something back as a ransom), which is not required in this sentence.