Thanks for your help.         

 But I want:        

Example: when I search it show 3 record, and I want to count this record.     (field count_record = 3)

Hello BB

It is already showing in odoo17 

Solution : 2

If you want to store in a field , You can also do like this

​ ​ ​
class SaleOrder(models.Model):
​_inherit = 'sale.order'

​no_of_records = fields.Integer(string='No. Of records', compute='count_no_of_records')

​def count_no_of_records(self):

​Solution : 1

​# records_lst = []
​# for record in self.search([], limit=10):
​# records_lst.append(record)
​# self.no_of_records = len(records_lst)

​solution:2 

​​len_records = self.search_count([])
​self.no_of_records = len_records

​ ​