Hi Rakesh,
You can't create legacy blob storage account via the portal, but you can create it via PowerShell using Cloud Shell. Below is sample code (resource group needs to exist before running):
New-AzStorageAccount -ResourceGroupName myresourcegroup -Name myblobstorageaccount -Location westus -SkuName Standard_LRS -Kind BlobStorage -AccessTier Hot
Create a storage account
https://learn.microsoft.com/en-us/azure/storage/common/storage-account-create?tabs=azure-powershell
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP