Which tutorial I should first complete before I can complete this tutorial?

Tutorials: https://developers.sap.com/tutorials/abap-s4hanacloud-procurement-purchasereq-shop.html
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Hi,

May I know which tutorial I need to complete first before I can complete this? On step 9 it mentions to open class zbp_i_online_shop_<###> which is not created as part of this tutorial. Is it possible to have link in the tutorial that can lead us to the pre-requisite tutorial so we can finish all the pre-requisite tutorials?

Thanks.