@Ravikumar Gundavaram , VNET integration is supported only in the Premium and Developer tiers of API Management. Refer Feature-based comparison of the Azure API Management tiers. For non-production environments, you can go with 'Developer' tier. However for production, you would need 'Premium' to have VNET integration which will cost bit higher. If your production is a low volume non-critical environment, you can still go with Developer tier, but keep in mind that you won't have any SLA in Developer tier.
Support for VNET in Basic Tier of APIM is a highly requested feature which is under review currently. Please feel free to upvote on it here.