Can I use DMS to move Oracle schemas on one EC2 instance to another EC2 instance?

Hello.

I think it is possible to specify an EC2 database as a DMS target.
https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.html

AWS Database Migration Service (AWS DMS) can use many of the most popular databases as a target for data replication. The target can be on an Amazon Elastic Compute Cloud (Amazon EC2) instance, an Amazon Relational Database Service (Amazon RDS) instance, or an on-premises database.

It seems that you need to create a schema etc. in advance as described in the document below.
https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.Oracle.html#CHAP_Target.Oracle.Limitations

AWS DMS doesn't create schema on the target Oracle database. You have to create any schemas you want on the target Oracle database. The schema name must already exist for the Oracle target. Tables from source schema are imported to the user or schema, which AWS DMS uses to connect to the target instance. To migrate multiple schemas, you can create multiple replication tasks. You can also migrate data to different schemas on a target. To do this, you need to use schema transformation rules on the AWS DMS table mappings.

By the way, if the amount of data to be migrated is small or if you can afford some downtime during migration, it may be easier to migrate using Oracle's native tools.
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Oracle.Procedural.Importing.DataPump.html