Folders in Azure blob storage don't really exists, meaning that, the folders in Blob storage are virtual and it is not supported to generate SAS at a folder level.
You can create different contains and provide SAS access to clients else create ADLS Gen2 storage account and in there get SAS for folder level.
See similar questions:
https://stackoverflow.com/questions/61879567/how-to-generate-a-shared-access-signature-for-a-folder-in-azure-blob-storage
https://stackoverflow.com/questions/37270955/is-it-possible-to-generate-sas-shared-access-signature-with-write-permission-f
Please don't forget to Accept Answer and Up-vote if the response helped -- Vaibhav