I am replacing these two switches with smart switches (Brand:Kasa). One of the smart switch is Single pole another is a 3-way switch. Both switches will need their neutral wires to be connected. My question is, can I connect neutral wires from both switches to this neutral wire as you can see?
Yes. Assuming I've traced it properly, those two switches both share the same hot, meaning they also share the same neutral:
You'll want to verify this by confirming that one breaker (one circuit) powers the lights (or other loads) that are controlled by both switches.
If not, you can simply use two different neutrals for the two smart switches. Looks like the wiring is non-metallic (NM) cable / romex-type, so you can just use the neutral that is part of the same cable as the other wires going to each switch.
Note that the white wire going to the 3-way switch is not neutral -- it's one of the two travelers (along with the red wire) for the the 3-way switch. Before disconnecting things you'll want to mark this to keep track of it.
For your smart switches, you can add two short lengths of white wire (pig tails) from the existing neutral bundle. You'll likely need to replace the wire nut with one rated for four 14-guage wires.