Do I need to have enterprise server in order to have multiple data sources in SSRS
There is no specific requirement for Enterprise Edition, though Express will not work either, which leaves Standard as your realistic option.

See Features Supported by the Editions of SQL Server 2008 R2.

Express Edition does have limitations:

Allowed data source SQL Server edition is SQL Server Express only.

The is no Remote and non-relational data source support.

Web and Workgroup have similar limitations.

You can see from that list there is no specific limitation against the number of Data Sources.