问个定语从句问题，请教，谢谢！

这句话转成陈述句语气应是the films were created in that era,although they are silent,they spoke volume.
for 表目的，为了。那是他们为那个时代所创造的。

定语从句里的介词词组，要把介词放在引导词的前面。所以，created for中，for置于which前。

they spoke volumes是指无声电影.
the films of the era is silent,but they spoke volume那个时代的电影尽管是无声的，但仍然给我们传递了大量的信息。

是create for。从句里如果动词短语有介词，要提到前面。如the way in which the word are put together

which 指的是前面的句子 先行词是句子 for表示的是目的

补充:
这个是带有定语从句的让步状语从句结构
句子的意思是
尽管胶片时代是无声的(无声电影) 但他们却向社会传递了大量的信息 这就是他们被创造出来的价值(这就是他们为什么会被创造出来)
Although the films of the era were silent 状语从句
they spoke volumes to the society 全句的主句
for which they were created. 结构松散的定语从句 (起补充说明作用,非限定)

此句主句为they spoke volumes to the society，前面although引导让步状语从句，for是因为create for中的for提前了。从句中动词短语中的介词可以前置（如果是短语动词则不行）。
其中共有三个句子：
1. 主句：they spoke volumes to the society.
2. although引导的从句： the films of the era were silent.
3. which引导的从句： they were created for (the society).