Mandarin equivalent of "㗎喇"?
㗎喇 is a combination of multiple Cantonese sentence final particles (SFPs):


㗎 gaa3 is a contraction of 嘅呀 ge3 aa3.

嘅 ge3 is directly equivalent to Mandarin's 的 de in meaning and usage.
呀 aa3 is used in Cantonese to soften the tone of a sentence. I don't believe Mandarin has a direct standardized equivalent to it, but some Mandarin speakers do use it in a similar manner.

喇 laa3 is directly equivalent to Mandarin's SFP 了 le. Both of these words are actually cognate to one another, ultimately having been descended from 來 (note that this only applies to Mandarin's sentence-final 了; its post-verb 了 le actually is descended from 了 liǎo). Mandarin chose 了 to represent this word; written Cantonese isn't very standardized, so people have variously represented it using the characters 喇, 嚹, or 啦.


Given this, the Mandarin equivalent could be 的了 de le. While I noted there was no direct standard Mandarin equivalent for Cantonese's 呀, some speakers do use it. In Mandarin though, it would be attached after 了 rather than after 的; like Cantonese, it gets contracted as well, changing 了 le to 啦 la; the final result would be 的啦 de la, as @Stan mentioned in his comment.