Change of yarn, selecting right needle size for tension

Hi. I have chosen a lovely pattern, ‘Laresca’ by Corrina Ferguson. The suggested yarn is Rowan Panama which is discontinued. That tension is 24 sts x 30 rounds = 4" with size 4mm needles.

I looked on a yarn substitute site and have chosen DMC Natura Linen instead which has a tension of 22 sts x 28 rows to 4" on a size 3.5mm needle.

Help! What do I do now? Thank you so much for any guidance from my knitting sisters in heart!

The replies here have given you some good ideas for how to start:

Use the DMC yarn to knit a test swatch. Cast on about 28sts and knit for 4 inches. You can measure the sts per inch over the center 4 inches. That’ll give you a good idea of gauge and of the feel and drape of the knit fabric. You can then adjust the tension if necessary by changing the needle size.