I personally use http://www.wpallimport.com/ with the ACF add on.
That being said, the best I can tell you is how repeaters are stored.
The repeater field itself is stored in the database with the field name, this is the same as the other fields you’ve already worked with. This field contains the number of rows in the repeater. Each subfield of the repeater is stored as {$repeater_name}_{$row}_{$subfield_name} with rows starting a 0.
The keys for these fields will be stored in another db entry starting with
field | field name in db | field key meta name |
repeater | repeater | _repeater |
row 1 subfield1 | repeater_0_subfield1 | _repeater_0_subfield1 |
row 1 subfield2 | repeater_0_subfield2 | _repeater_0_subfield2 |
row 2 subfield1 | repeater_1_subfield1 | _repeater_1_subfield1 |
row 2 subfield2 | repeater_1_subfield2 | _repeater_1_subfield2 |
etc....
Hopefully you don’t have any nested repeaters, but the pattern continues. A nested repeater will have the number of rows in the above field and then it’s own sub field
{$repeater_name}_{$row}_{$nested_repeater_name}_{$row}_{$subfield_name}
