from odoo import models, fields, api

class StockMove(models.Model):

@api.multi
    def get_data(self):
        data = self.env['sale.order.line'].search([])
        print("Get Data Function")
        for rec in data:
            print(rec.x_serialnumber)
            for record in self:
                record.x_serialnumber = rec.x_serialnumber

    _inherit = 'stock.move'
    x_serialnumber = fields.Text(string="Serial Number", compute='get_data')"

On Sale order line it shows like this:

Serial Number: in both lines

112233

445566

But in stock move:

Serial Number: in both lines

445566

445566