Usually with long haired cats it's pretty obvious when they are kittens, they usually have pretty long fur even as kittens
My avatar cat: Tesla as an 8 week old kitten:
Welcome to you and Oilve to TCS
She's a pretty girl. From your photos, she looks like DMH Ginger Tabby.
Feel free to ask questions as you've come to the right place. There are many here with years of experience with cats can help answer your questions. Also do look through the site for the many interesting and helpful topics.
Please post more of Olive's photos