Dear Udanee, I don't think there are H indexes. However, the quality of the conference can be inferred by the bodies that organise them. For example the peak academic marketing body is the American Marketing Association https://www.ama.org/events-training/Conferences/Pages/default.aspx?k=contentsource:%22Main%22%20AND%20(ContentType:%22AMAConferencePage%22%20IsDocument:1%20)&r=AMAMergedEventDate%3E=2/21/2018
or the Academy of international Business for international business https://aib.msu.edu/events/2018/