I would like to know how many public libraries in Finland are located in shopping malls? Best regards,

I am sorry to say I was not able to find record that simply lists public libraries located in shopping malls. To form the answer would require gathering the address of every library and finding out whether there is a shopping mall or not. According to the website Kirjastot.fi (Libraries.fi) there is at least one library in every municipality which makes the total amount of public libraries nearly 800 (mobile libraries not included). Here is a link to the website's statistics page https://www.libraries.fi/statistics. You will also find there access to the whole statistics database of public libraries.

However, in general, there is an ever rising trend whenever a new public library is established or an old one relocated to situate them into shopping malls or community centers or close to them so that they would be easily accessible. 

In Helsinki Metropolitan Area (Helmet) there are nearly 70 libraries of which about ten are in a shopping mall and community centers. (Correction to the last sentence: About ten libraries are in shopping malls but there are more libraries in community centers.)

References:

Libraries.fi. https://www.libraries.fi/