Extract values between certain conditions

Hi, how are you today?

I need to extract a name between certain conditions in a large string and put them in a new cell. See this real example:

a:3:{s:7:"form_id";i:829;s:9:"form_data";a:11:{s:9:"__form_id";i:829;s:7:"__refer";s:43:"https://acme.com/mapa-cabalistico";s:9:"__is_ajax";b:0;s:7:"post_id";s:3:"708";s:12:"preco_padrao";s:5:"29.90";s:10:"field_name";s:26:"Maria Clara da Silva";s:15:"field_nomeatual";s:26:"Maria Clara da Silva";s:22:"field_datadenascimento";s:10:"11/08/1996";s:16:"field_assinatura";s:0:"";s:11:"field_preco";s:5:"29.90";s:10:"field_name";s:0:"";}s:8:"settings";a:12:{s:15:"product_id_from";s:6:"manual";s:14:"product_manual";a:1:{i:0;a:1:{s:2:"id";s:3:"822";}}s:8:"wc_price";s:11:"field_preco";s:24:"wc_heading_order_details";s:17:"Mapa Cabalístico";s:33:"wc_fields_map__billing_first_name";s:0:"";s:27:"wc_fields_map__billing_city";s:12:"field_cidade";s:28:"wc_fields_map__billing_state";s:12:"field_estado";s:34:"wc_fields_map__shipping_first_name";s:15:"field_nomeatual";s:33:"wc_fields_map__shipping_last_name";s:0:"";s:29:"wc_fields_map__order_comments";s:0:"";s:30:"wc_fields_map__billing_company";s:10:"field_nome";s:32:"wc_fields_map__billing_address_1";s:22:"field_datadenascimento";}}

A name, in this example, "Maria Clara da Silva" is associated to "field_name". The text "26" before the name is not always the same. This number may change in the other strings. The same is true of the text number "15" after the name. This number may change in the other strings. The length of string may change, so, I can't use length to remove or extract the name.

I don't find a way to make this task in one single event or form.

Maybe you can help me because I haven't found a way to do that.