This might be yours:
Here's a "F.H. Hackbart", born c.1842, arriving in NY on 20 June 1868 aboard the "Humboldt" out of Hamburb. http://castlegarden.org/quick_search_detail.php?p_id=5247223
The Hamburg Passenger List has the same info, and gives "Langenhagen, Prussia" as his residence in Germany. If you have access to Ancestry, you can look at the original page, which as a mark connecting him to the next name which looks like "Wilh (Wilhelm) Hepp (possibly Hopp)", born 1840. That mark usually means they were family, or at least traveling together.
As a guess, this might be his naturalization index card https://familysearch.org/pal:/MM9.3.1/TH-1-14904-43141-83?cc...