Fresco is not designed to create Vector images which makes the enlarging process quite difficult.
Are you sure you managed to creat a document of 3200cm The largest I can achieve is 288.996 on both W & H.
My personal approach would be to set the highest ppi you can with the highest proportional Width and Height that you can achieve in relation to the final size you need. Or if possible create the images you want to use then export them to an app which can work in the size that you want.
Thank you for your message and advice regarding this, it is very helpful thank you.
I have decided to instead use Adobe Illustrator on my MacBook Pro where I am able to create my illustration at 3200cm x 1200cm and at 300dpi.
I regards to dpi, is there a general rule or equation that converts dpi into printed sizes?
I am aware 300dpi allows a high resolution image for an A4 page for example, however can 300dpi images be printed at larger sizes successfully, or are there other dpi recommended for certain paper sizes?