@Isabella the easiest way I know would be through SDF - using XML to create all those fields in one shot. https://developers.suitecommerce.com/get-started-with-the-suitecloud-development-framework-sdf-and-suitecommerce.html

<itemcustomfield scriptid="custitem_mynewfield">
    <accesslevel>2</accesslevel>
    <appliestoinventory>T</appliestoinventory>
    <displaytype>NORMAL</displaytype>
    <fieldtype>TEXT</fieldtype>
    <label>My New Field</label>
    <searchlevel>2</searchlevel>
    <storevalue>T</storevalue>
</itemcustomfield>

Oh wow cool! I've never done that before... I'll have to read up on how to actually load a script!