Hi there!
Write in the plural.
1. This is my pencil. - These are my pencils.
2. This is my robot. These are my robots.
3. This is a backpack. -These are backpacks
4. This is my friend. - These are my friends.
5. This is your pencil. -These are your pencils.
6. This is her flower.-These are her flowers.
7. This is his book-These are her books.
________________
adjective/pronume demonstrative
this-acesta/aceasta----> these-acestia/acestea
that-acela/aceea------> those-aceia/acelea