pos/pos_require_product_quantity/views/pos_config.xml

<?xml version="1.0"?>
<odoo>

    <record id="view_pos_config_form" model="ir.ui.view">
        <field name="name">pos.config.form.view.inherit</field>
        <field name="model">pos.config</field>
        <field name="inherit_id" ref="point_of_sale.pos_config_view_form"/>
        <field name="arch" type="xml">
            <xpath expr="//field[@name='restrict_price_control']/../.." position="after">
                <div class="col-xs-12 col-lg-6 o_setting_box" >
                    <div class="o_setting_left_pane">
                        <field name="require_product_quantity"/>
                    </div>
                    <div class="o_setting_right_pane">
                        <label for="require_product_quantity"/>
                        <div class="text-muted">
                            Show pop-up when product quantity is set to 0 for one or more order lines when clicking on "Payment" button.
                        </div>
                    </div>
                </div>
            </xpath>
        </field>
    </record>

</odoo>