Where is the tail light fuse inside the fuse box inside the car? No lid for the diagram :(

Try these two web links. The first is a diagram of the fuse box. the second is how to find and open the fuse box cover. It is inside the vehicle, on top of the dashboard, directly above the radio and centre console. I think it is fuse 6 you need to check. The label on the under side of the fuse box lid might have it marked as "TAIL".
*Note* ALWAYS replace fuses with the same colour and rating. They are set up to a certain amp level for safety.
I think yours is a 15A Blue blade fuse.
https://www.autogenius.info/toyota-previa-first-generation-mk1-xr10-xr20-1990-1999-fuse-box-diagram/

https://youtu.be/omtQ1UdqjhI

Have you checked the bulbs and fuses? The fuse box for them is under the bonnet, usually near the battery. The lid normally just unclips. Try fuses 13, (brake lights), 22 (right), and 23 (left) for the tail lights. Always replace fuses with the same colour and rating.
I think on your model the bulbs are fairly simple to get to. Fold the small cover inside the boot out of the way. The bulb board is simply clipped into place. Bend the two clips inwards and wriggle it out past the boot liner. The bulbs are just a small turn Anti-clockwise and It slides out.
I've attached links to a fuse box diagram and a YouTube video for the rear lights.
https://fusesdiagram.com/volkswagen/fuses-and-relay-volkswagen-passat-b5.html

https://youtu.be/fHxaLhpWM0s

What is year--make--model? Is the fuse box labeled or the fuse box lid? Does your owners manual have this info?

have a look at fuse box a list of what fuse does what will be on inside of lid

I think you can change a good tail light for your car.

the park lamp, tail lamp fuse is located in the underhood fuse box the location of fuses in that box isprinted on the inside of the fuse box cover

you have 2 fuse boxes , one by the driverside left foot 9called the kick box and 1 under the hood located on the driver side. both have a diagram of what each fuse and relay go to ,on the underside of there lids, you also have a diagram in the owners manuel. check the fuses first if the problem still exist then check for loose connection s if the problem is unresolved you probley have a short. if both the tail lights and the dash lights whent at the same time id go with a short .

the layout for the fuses should be under the lid of the fuse box itself and the relay box it is normally imprinted right on the top and a diagram under the lid also

http://www.carfusebox.com/suzuki-forenza-2005-under-dash-fuse-boxblock-circuit-breaker-diagram/