Here's how field data storage structure looks like since version 2.0 ("{key}" references unique key of field without brackets):
Checkout Fields:
| Meta key | Meta value | Location |
| _wccf_cf_{key} | field value | in order meta |
| _wccf_cf_id_{key} | field id | in order meta |
| _wccf_cf_data_{key} | extra data array | in order meta |
| _wccf_file_{access_key} | file data | in order meta |
Order Fields:
| Meta key | Meta value | Location |
| _wccf_of_{key} | field value | in order meta |
| _wccf_of_id_{key} | field id | in order meta |
| _wccf_of_data_{key} | extra data array | in order meta |
| _wccf_file_{access_key} | file data | in order meta |
Product Fields:
| Meta key | Meta value | Location |
| _wccf_pf_{key} | field value | in order item meta |
| _wccf_pf_id_{key} | field id | in order item meta |
| _wccf_pf_data_{key} | extra data array | in order item meta |
| _wccf_file_{access_key} | file data | in order item meta |
Product Properties:
| Meta key | Meta value | Location |
| _wccf_pp_{key} | field value | in product meta |
| _wccf_pp_id_{key} | field id | in product meta |
| _wccf_pp_data_{key} | extra data array | in product meta |
| _wccf_file_{access_key} | file data | in product meta |
User Fields:
| Meta key | Meta value | Location |
| _wccf_uf_{key} | field value | in user meta |
| _wccf_uf_id_{key} | field id | in user meta |
| _wccf_uf_data_{key} | extra data array | in user meta |
| _wccf_file_{access_key} | file data | in user meta |