Squid proxy server with 3G mobile dongle

Dear All,
i'm running ubuntu 18.04 on my Odroid XU4 and i have connected to internet using 3G mobile dongle. i have installed squid proxy server but i have no clue how to set up proxy ip ( i have set my port to 8080)
my Code:ifconfig reads as below

Code:root@odroid:~# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.42.0.1 netmask 255.255.255.0 broadcast 10.42.0.255
inet6 fe80::466:800f:cd03:77ce prefixlen 64 scopeid 0x20<link>
ether 00:1e:06:32:e3:00 txqueuelen 1000 (Ethernet)
RX packets 1006050 bytes 1074956359 (1.0 GB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2152643 bytes 3038443982 (3.0 GB)
TX errors 0 dropped 8 overruns 0 carrier 0 collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 2820 bytes 395944 (395.9 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2820 bytes 395944 (395.9 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

wwan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.158.81.175 netmask 255.255.255.224 broadcast 10.158.81.191
ether 00:1e:10:1f:00:00 txqueuelen 1000 (Ethernet)
RX packets 65366 bytes 72974764 (72.9 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 35547 bytes 6375709 (6.3 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0pls tell me which ip to be used in "IP:8080"

is it 127.0.0.1 or 10.158.81.175 or just 10.42.0.1

i have tried with 127.0.0.1 but none of proxy rules that i have set seems to not working....

can i put my visbile hostname instead of an IP?

pls help me