@rnulanmoo
Start off small - so hand under chest or however you’re picking up, treat... wait till that’s something that’s good and exciting and do the next bit and treat... it might take a few days, might take longer.
But also, yeah think about how and why you’re picking him up - do you need to?
A growl isn’t aggression, it’s just a noise that means, I really don’t like this. For some dogs with being picked up it’s scary, for some it’s actually that how it’s being done is uncomfortable... with puppies it’s often just - hoy, I’ve got legs!!! I can do it, stop mithering me!!!
You never want to tell a dog off for growling, that can actually create issues because you’re not changing how they feel, so if you stop them growling and they still want something to stop, that’s when they might escalate it... if they unhappy about something and they growl, back off and then look at how you can make them comfortable with what you need to do.