I want to increase the size and buy upto 4GB.

I think you are getting storage and memory mixed up.

Your answer to @Gary shows you have a 30GB volume attached, which sounds right.

Your question talks about 1GB storage, when I think you actually mean 1GB of memory for your EC2 instance. In the EC2 section of AWS Console, find your instance and what is the Instance type ?

If you want to uplift this from an instance with 1GB memory to an instance with 4GB memory then this is certainly possible https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-resize.html

In general you can uplift to another instance type within the same instance family, so e.g. t2.micro (1CPU, 1GB) to t2.medium (2CPU, 4GB), and in some cases you can move to a different instance family, but that gets more complicated.

Bear in mind that the bigger the instance, the more it will cost https://aws.amazon.com/ec2/pricing/on-demand/

Also, if you are currently using an instance type that is in scope of Free Tier, then uplifting that instance will mean that the new instance is outside of Free Tier, and you will find yourself paying for something that you previously got for free.

Please clarify the “Storage” you mention. It’s not clear what storage service you are using.

If it’s S3 then you don’t need to buy any more storage, you pay for what you consume.