Please make sure all products are lined up in a row.
Literal
Certainly all products [subject-が] one-row [in-に] lining-up [manner-ように] [polite-request-ください].
商品 (しょうひん, 'products/merchandise') is more commercial in tone than the general 品物 ('items'). ~ようにしてください is a polite request to ensure a certain state — 'please make sure that...'