Hi.
On your 98 Dakota.
Is equipaded with a single Flasher.
If you replace all ready.
Check the FUSE # 10, 15 amp..
On the Fuse box. left side of Dash.
and the FUSE D 25, amp. On engine compartment Fuse box.
Check the proper funtion of the HAZARD switch.
Bacause if the Hazard switch is bad the turn signal don't will work. Match the OLD flasher with the New one.

If after of this still not work.
Remove the steering wheel cover, locate the Turn signal switch connector and with a TEST Light check power with the Key ON
12v. to the RED wire and PINK wire..
If you found 12v. check the connection with the switch.
If the connection is good. you will need to replace the turn signal switch.
But if you don't found 12v. You need to look a an open circuit.
And fix it..

I hope this help on your problem..
Thank you for use fixya...