Ecommerce / Inventory Management / order fulfillment/ accounting

Hi,
Looking for some help… We are now exploring ecommerce on both a business to business platform and direct to consumer. We have been looking at a lot of different software that is available and hoping we could maybe piece together something with Infusionsoft. The main things I think we are missing are inventory management, order fulfillment. Can anyone give us some direction. Many thanks in advance…